Frequency-responsive signal-receiving apparatus



Nov. 4, 1930.

w. BRUCKEL E AL 69 FREQUENCY RESPONSIVE SIGNAL RECEIVING APPARATUS Filed April 23, 1925 Inventors WaLdemar BriickeL Robert SchLrnpF gy M/% 54;

TheLrAUL'ornqy Patented Nov. 4, 1930 ries as the frequency is varied above or cuit is tuned. We make use of this for operating relays or UNITED STA ES P ATENT OFFICE v wannmn mzflcxm. m 30mm scams, or 3mm, ennxm,

816N038 TO emnnr. ELECTRIC comm, a conromrron or NEW YORK FREQUENCY-31282011811713 srcnarrimcnzvme urmrus Application fled April :3, ms, Serial m. 25,451, and in Germany August 5; me.

Our invention relates to a frequency responsive signal receivin apparatus suitable or reproducing telemetric indications.

It is sometimes desirable to transmit the indications of measurin -instruments to a distant point and reproduce the indications at such points. This is of special importance in the oint operation of a number of electric power stations suppl ing a common distribution system where t e system is supervised from one control station. It ma also be desirable to provide automatic 10a control with the same apparatus. Where the power stations are considerable distances apart, the expense of separate control wires between them becomes an important consideration and in such cases it may be preferable to make use of the existing power lines'or one phase of an existing power line and a ground return.

It is known that high frequency currents,

commonly called carrier currents, may be imposed upon a commercial frequency or a direct current power circuit without interference for the purpose of sending signals, the signal receiving a paratus being responsive only to the high requency carrier current. The receiving apparatus which forms the subject of our invention is particularly designed for this kind of service.

According to our invention, the receiving apparatus includes an oscillation circuit having inductance and capacity connected in series with the high frequency signallin circuit the signalling currents of whic are suitably amplified where that is necessary.

It is known that where inductance and capacity are connected in series with a variable requency voltage, the relative voltage drop across the inductance and the capacit vaelow the resonance frequency for which the cirphenomenon to control a differential relay thedifferential coils of which are respectively connected so as to have currents proportional to the voltage drop across the two parts of the receiving circuit. The c eration of this relay may therefore be ma e responsive to changes in the signalling frequency for a given resonance condition of the receiving circuit. Where the apparatus is to function as a telemetric receiving and indicating device, either the inductance or the capacity is made adjustable for the urpose of changing the resonance setting of the circuit. The differential relay is then made to'control the position of the indicator for changes in frequency and simultaneously to tune the receiving circuit to a condition .of resonance after each change in the signalling frequency. The features of our invention WhlCll. are believed to be novel and patentable will be pointed out inthe claims appended hereto. For a better understanding of our invention, reference is made in the following description to the accompanying drawing which illustrates the preferred arrangement of our improved receiving devibe as used as a telemetri'c receiver.

Referring to the drawing, 10 indicates a conductor which may be one phase of a polyphase distribution system extending to a distant station. Between this conductor and ground is connected a circuit containing a condenser 11 and a high frequency re ceiving amplifier 12. It will be understood that high frequency carrier currents are transmitted through this circuit and that the frequency is varied in any suitable manner in accor ance with the signals to be transmitted.

The present invention has to do with the receiving apparatus only and consequently the transmitting apparatus will not be described. In general the transmitter may be similar in operation to the receiver. A de- 'scription of a suitable transmitting device for this purpose may be found in a co ending application, Serial N 0. 721,341, filed une 20 1924, of B. W. S 1,718,497, issued June 25, 1929, entitled Telemetric system, which application is assigned to the same assignee as the present invention. The amplified receiving circuit shown at 12 contains a condenser 14 and a reactance 15 connected in series. '1 he condenser 14 is here represented as being adjustable, how

ever it will be evident that the inductive react t. Clair, now Patent No.

ance might be the adjustable element ofthe circuit instead of the condenser and in certain cases the circuit need not be made adjustable.

Connected across the condenser 14 is the gridand cathode circuit of a tube 16 connected' as a rectifier,'and similarly connected across the reactance 15 is the grid and. cathode circuit of a tube 17. The cathodes of the tubes areconnccted to the negative pole of a battery 18. Between the other pole of this battery and the plates of the tubes 16 and 17 are se 'arately connected thecoils 19' and 20 of a ifferential relay, the pivotally mounted armature of which is represented j The relay armature is provided with a contactclosing lever 22 cooperatin with circuit closing contacts 2?; and 24, W ich contacts are biased to an open position when therelay armature isin a central position. The armature 21 is normally biased to the central position represented by a spring 25. Coil '19 tends to turn .the armature and its lever in a counter clockwise direction and, coil 20 tends to turn the armature in the opposite direction. When these two coils are deenergized or are equall in the central positlon represented.

The receiving circuit is so proportioned that it ma be tuned to a condition of resonanceaby t e adjustable condenser 14 for any ire uency of the received signalling current wit in the range of signalling frequency selected. :When so tuned, the voltage drops across the condenser 14 and inductive reactmice 15 are equal or substantially equal and as a consequence, the plate currents of the two tubes 16 and 17 are equal. When the signalling frequency is increased above'the resonance frequency of the receiving circuit for a given setting of the condenser 14, the

' volta e drop across the inductive reactance armature 21 in a counter clockwise direction P to close contacts 23. It will be evident that 15 M11 be higher than that across the condenser and as a consequence, the current in the plate circuit of tube 17 will. be hi her than that in the corresponding circuit 0 tube 16. 1

Coil 20 will then'predominate over coil 19 and rotate the armature 21 in a clockwisedirection closin contacts 24. If the frequency is decreased elow that corresponding to a condition of resonance, the voltageacross the condenser 14 will be higher than that across the inductive reactance and as a result coil 19 will predominate over 'coil 20 to rotate if the apparatus is merely used to operate the relay, it will not be necessary to adjust the resonance settin of the receiving circuit. However if use as a telemetric receiving apparatus the resonance setting of the receivin current will be changed as the signalling requency is changed in response to some remote indicating device and simultaenergized, the armature stands neously there will be operated a receiving indicator calibrated with the apparatus to reproduce the distant indication.

For this purpose the contacts 23 and 24 control the energizing circuit of a reversible motor26 sup lied from a suitable source 27.

The plates 0 the condenser 14 are relatively adjusted by this motor, and simultaneously with this adjustment a ointer 28 is moved relative to a scale 29. ne plate of the condenser maybe made stationary and the other movable by means of a worm gear 30 driven by the motor 26. This worm gear drives a shaft 31 .to which the pointer 28 and the movable part of the condenser is secured. The condenser plates may be so she. ed as to obtain an exact or proportional efiection between thesending and receiving indicators and the scale 29 raduated accordingly. The

motor "26 might e used to operate any other type of indicator or signal or a load control of resonance with the new frequency. For

the condition assumed, the capacity of the condenser should be increased and with the arrangement illustrated, the pointer 28 will then be moved to the right. As soon as the resonance condition is reached, contacts 23 are opened and the motor stopped. An increase in si alling fre none will cause the motor 26 to e operat in t e opposite direction, moving the ointer 28 to t e left, until a resonance con ition is again established. The apparatus is thus caused to reproduce an indication corresponding to the transmitted frequency. Usual arrangements for obtaining sharpness in tuning and fine adjustments may be employed.

In accordance with the provisions of the patent statutes, we have described the principle of operation of our invention, together with the apparatus which we now consider to re resent the best embodiment thereof; but

we esire to have it understood that the aparatus shown and described is only illustrative and that the invention may be carried out by other means.

.' What we claim as new and desire to secure by Letters Patent of the United States is,:-

1. A. frequency responsive signal receiving apparatus comprising a signal receiving circuit having an inductive reactance and a cagacitive reactance connectedin -series, a relay not aving a pair of difierentially connected ooils m plate electrodes,

means responsive to the voltage across the capacitive rcactance for energizin one of said coils, means responsive to the v0 tage across the inductive reactance for energizing the other coil, and means including said relay for controlling one of said reactances in accordance with the frequency of the received current.

2. Frequency responsive signal receiving apparatus comprising a signal receiving circuit having an inductive reactance and a capacitive reactance connected in series, a pair of thermionic tubes having filament grid and a circuit connecting the filament and grid of one tube across the capacitive reactance, a circuit connecting the filament and grid of the other tube across the inductive reactance, a relay havinga pair of difi'erentially wound coils respectively connected in the plate circuits of said tube, and means including said relay for control-' ling one of said reactances in accordance with the frequency of the received current.

3. A frequency responsive signal receiving apparatus comprising a signal receiving circult, an inductive reactance and a capacity connected in series in said circuit, a rela responsive to the difference in the voltage rops across said inductive reactance and capacity, and means controlled by said relay for varying the relative values of said inductive reactance and capacity to maintain a condition of resonance at the frequency of the received signal current.

4. Frequency responsive si apparatus comprising a signa cult having an inductive reactance and a capacity connected in series, a relay having a pair of difierentiall connected coils, means responsive to the v0 tage across the capacity for energizing one of said coils, means responsive to the voltage across the inductive reactance for energizin the other of said coils, and means control ed by said relay for varying the relative values of said inductive reactance and capacity.

5. Frequency responsive si apparatus comprising a signs curt, an inductive reactance and a capacity connected in series in said circuit, a relay having a pair of diflerentially connected coils,

a1 receiving al receiving receiving cirapair of thermionic tubes connected to energlze said coils in response to the voltages across said inductive reactance and capaclt respectively, and means controlled by sai relay for varying the relative values of and inductive reactance and capacity.

6. Frequency responsive signal receiving apparatus comprising a si a receiving circmt containing an inductive reactanceand a capacit connected in series, means for ad- ]ustmg t 0 relative values ofsaid inductive reactanoe and capacity for tuning said circuits, a relay responsive to the di erence in the voltages'across said inductive reactance receiving cirand capacity for controlling said tuning means to establish a condition oi resonance upon a change in the frequency of the signalling current, and a position indicator moved by said tuning means.

7. Frequency responsive si ti receiving apparatus comprising a signs. receiving circuit containing tuning means, a motor i'or operating said tuning means, a position indi cator operated by said motor, and a relay responsive to an untuned condition of said signal receiving circuit, as regards the ire quency of the signalling current, for controlling said motor in a manner to tune said circuit to a condition of resonance.

8. Frequency responsive signal receiving apparatus comprising a signal receiving cir= curt containing an inductive reactance and a variable condenser connected in series, a reversible electric motor for adjusting the set ting of said condenser, contacts for enor ing said motor in either direction, a re ay controllin said contacts, said relay having coils whic are energized difi'erentially in response to the voltages across said condenser and inductive reactance to maintain said contacts open when said circuit is in a condition of resonance, and to close said contacts in the proper direction to bring said circuit back to a condition of resonance whenever the frequency of the si ailing current changes.

In witness w ereof, we have hereunto set our hands this 4th day of April, 1925.

' WALDEMAR BRUCKEL,

Du. ROBERT SGHIMPF. 

